Add support for controlling amount of nodes

Nodes spun up in Gcloud defaults to '3' nodes
This number can be a lot considering the QA
autodevops spec does not need this many nodes

qa/qa/runtime/env.rb

@@ -181,6 +181,10 @@ module QA
         ENV.fetch('GCLOUD_REGION')
       end
+      def gcloud_num_nodes
+        ENV.fetch('GCLOUD_NUM_NODES', 3)
+      end
+
       def has_gcloud_credentials?
         %w[GCLOUD_ACCOUNT_KEY GCLOUD_ACCOUNT_EMAIL].none? { |var| ENV[var].to_s.empty? }
       end

qa/qa/service/kubernetes_cluster.rb

@@ -30,6 +30,7 @@ module QA
           --enable-basic-auth
           --region #{Runtime::Env.gcloud_region}
           --disk-size 10GB
+          --num-nodes #{Runtime::Env.gcloud_num_nodes}
           && gcloud container clusters
           get-credentials
           --region #{Runtime::Env.gcloud_region}